Process for the removal of undesirable sulphur compounds from petroleum oil



March 14, 1944. J HONBERG 2,344,418

,.R. sc PROCESS FOR THE REMOVAL OF UNDESIRABLE SULPHUR C OMPOUNDS FPETROLEUM OIL Filed OQt. 1940 2 Sheets-Sheet l March 14, 1944.

J, R. scHoNBERG 2,344,418 PROCESS FOR THE REMOVAL OF UNDESIRABLESULP-HUR COMPOUNDS FROM PETROLEUM OIL Filed Oct. 5, 1940 2 Sheets-Sheet2 7,20 PANE LINE A "Varona zap nomme oorLlr will Ffa-2 WEA TE a OILOUTLE T Patented Mar. 14, 1944 PROCESS FOR THE REMOVAL OF UNDESIR- ABLESULPHUR COMPOUNDS FROM PE- 'rnoLEUM oIL Jackson R. Schonberg,

to Standard Oil Deve poration of Delaware Westfield, N. J., assignerlopment Company, a cor- Application October 5, 1940, Serial No. 359,840

(Cl. 19E-31) 1 Claim.

The present invention relates to a process' for the treatment of mineraloils. The invention is more particularly' concerned with an improvementin the treatment of petroleum oils for the removal of objectionablesulphur compounds therefrom with sulphuric or a similar acid underconditions in which unsaturated constituents are retained in the oil. Inaccordance with the present process, deleterious sulphur compounds areremoved from petroleum oils boiling in the motor fuel boiling range .bytreating these oils with sulphuric or an equivalent acid andsimultaneously agitating the mixture, controlling the temperature, andremoving the heat of reaction by vaporization of a refrigerantthroughout the mass of the oil.

It is well known in the art to treat mineral oils, particularlypetroleum oils boiling in the motor fuel boiling range, with sulphuricor an equivalent acid in various rening and manufacturing operations. Aconventional method for removing undesirable sulphur compounds frompetroleum oil fractions is to treat the same with sulphuric acid. Thismethod is not entirely satisfactory since the acid not only removes the'undesirable sulphur compounds, butalso tends to polymerize and remove`valuable hydrocarbon constituents which materially improve the qualityoi the nished motor fuel. The loss of valuable constituents, due to theeffect of sulphuric acid, varies widely; depending to a large extentupon the strength of the acid, the character of the stock being treated,vand the temperature of treatment. However, when contacting the oil withacid at atmospheric temperatures under normal procedures, Vthe loss whenmeasured in terms of yields, lower clear octane numbers, and poorersusceptibilities of the iinished stocks for knock suppressing agents isconsiderable in every instance. In order tovovercome these disadvantageswhich are inherent in usual current4 processes utilizing sulphuric acidfor the removal of objectionable sulphur compounds from petroleum oils,various modications and different procedures have been suggested. Forexample, it has been proposed to employ relatively weak acids Theseprocesses are not particularly desirable since it materially impairs theeiiiciency of the operation with respect to time required, dailycapacity of the equipment, and the degree to which the objectionablesulphur compounds are removed. It has also been suggested that variousdiluents be utilized or that the treating operation be conducted atrelatively low temperatures in the range from about 40 F. to 20 F. orbelow. At these temperatures the sulphuric acid apparently dissolves theundesirable sulphur compounds and will not dissolve or attackconstituents which it is desired to retain in the finished motor fuel.These low temperature operations are not entirely satisfactory due toinherent diliiculties and expenses involved in operating at temperaturesappreciably below '70 F. to 80 F. Furthermore, at these low temperaturesthe activity of the acid in removing objectionable sulphur compounds,particularly when employing sulphuric acid, is considerably impaired,thus necessitating a material increase in the amount of acid required tosecure a given sulphur reduction per given volume of oil being treated.

I have now discovered an improved process for removing objectionablesulphur compounds from petroleum oils containing the same. I havediscovered that material benefits are secured with respect to sulphurremoval and objectionable side reactions avoided, provided the heat ofthe reaction is immediately removed at the instant the acid reacts withthe objectionable sulphur compounds which are being removed. Inaccordance with my invention a refrigerant is vaporized throughout themass in order to remove the heat of reaction evolved and to maintain thetemperature of the reaction somewhat below about F. By operating in thismanner, excellent mixing is secured and local overheating prevented.Furthermore, the body of the oil is maintained at substantially aconstant temperature which permits treatment of the oil at highertemperatures where the activity of the acid in the removal of theobjectionable sulphur compounds is not impaired and under conditionswhere deleterious polymerization of valuable oil constituents will notoccur.

The process of my invention may be readily understood by reference tothe attached 'drawings ,illustrating preferred modifications of thesame.

Figure 1 illustrates a process used in conjunction with an overallrefining operation while Figure 2 illustrates a, preferred type of acidcontacting stage. Referring specically to Figure 1, a feed oil, whichfor the purpose of illustration is assumed to be a petroleum crude oil,is introduced vinto distillation Zone l bymeans of feed line 2.

Dstillation zone I may comprise anyA suitable number and arrangement ofdistillation units. Temperature and pressureV conditions are adjusted toremove relatively high boiling constituents by means of lines 3 and 4,and to remove overhead by means of line 5 hydrocarbon constituentsboiling in the motor fuel boiling range. The overhead fraction is passedthrough condenser 5 and then introduced into separation zone 'I whereinuncondensed hydrocarbon constituents are separated from thecondensateand removed overhead by means of line 8. The condensate is Withdrawnfrom separation zone I by means of line 9 and introduced intostabilization zone I5,- Wherein temperature and pressure conditions areadjusted to completely free the, hydrocarbon constituents boiling in theInotorfuel boiling range of undesirable low boiling hydrocarbonconstituents such as propane and the like which are removed overhead bymeans ofline II and disposed of as desired. The stabilized product isWithdrawn from stabilization zone I0 by means of line I2l and passedinto acid treating zone I3. In this zone the oil, in accordance with thepresent invention, is intimatelycontacted with a mixture of acidandrefrigerant which is introduced into acid treating` zone I3 by meansofV lines I4 and I5. Acid treatingY zone I3 may comprise any number ofstages or units arranged in any desirable manner. The acid sludgecontaining the objectionable sulphur compounds is Withdrawn from acidtreating zone I3 by means of line I5 and handled in any mannerdesirable. The acid oil, free of acid sludge, is Withdrawnl from acid'treating zone I3 by means of line IIV and passed into neutralizationzone I8 in which the oil is neutralized with a suitable alkali such as acaustic solution which is introduced by means of line I9 and Withdrawnby means of line 2D; The neutralized acid oil is then passed toredistillation unit 2| by means of line 22., in which temperature andpressure conditions are adjusted to remove overhead by means of line 23a product having the desired end point. The overhead distillate iscondensed in condenser 24 and passed to storage or other- Wise handledby means of line 25; Unvaporized constituents are Withdrawn fromdistillation'zone 2l by means of line 25v and disposedA of` as desired.

A preferred modification of the present invention, particularly whenemployinga liquefied normally gaseous hydrocarbon as a refrigerant,is'to segregaten the refrigerant from the overhead vapors removed bymeans of line II in a separation zone 21. regate a propane stream bymeans of line 28, and an ethane stream by. means of line 29. The propanestream-may be introduced into the acid by meansof line 28 or withdrawnfrom the system by means of line 3i). preferred to condense the ethanestream by condenser 3I or other suitable means and to pass the same to aseparation zone 32 from which uncondensed constituents are Withdrawn bymeans of line 33. This condensed ethanestream is then introduced intothe acid by means of line 34.

Another preferred adaptation vof the present invention, particularlywhen` operating as described above, isto stabilize the oil during acidtreating rather than prior to acid treating. If this preferredadaptation of the invention be utilized, the condensate Withdrawn fromthe separation zone 'I by means of line 9 is passed directly into acidtreating zone I3 by means of line 35, and the neutralized acid oil ispassed through stabilization zone 35 by means of line 37 in Whichundesirable constituents are removed overhead by means ofY line 38 andthe stabilized product removed by means of line 39.

Figure 2 illustrates a preferred modification Conditions are adjusted t0seg- However, in general it is of the present invention and discloses indetail a method of contacting the feed oil with sulphuric acid andsimultaneously agitating the mixture and removing the heat of reactionby vaporization of a refrigerant. Treating vessel 50 comprises treatingstages M and N. Feed oil containing objectionable sulphur compounds isintroduced into stage N by means of line 5I. This oil upon entry intostage N simultaneously contacts acid Withdrawn from stag M by means ofline 52 and a refrigerant, Which for the purposes of description isassumed to be propane, which. is introduced by means of line 53.Pressure conditions are adjusted in stage N so that a sufficientquantity of propane is remo-ved at a rate so as to remove the heat ofreaction as it is evolved. The temperature of the oil introduced intostage N by means of line 5I, therefore, remains substantially constant.The vapor-ized propane is Withdrawn from stage N by means of line 54andhandledin any manner desirable, usually condensed and recycled tothel system. The treated oil flows into the bottom. of stage N in whichthek acid sludge separates and is Withdrawn from stage N by means ofline 55. TheV treated oil is Withdrawn from stage N` by means of pump 56and 1ine-51 and introduced into stage M. This oil simultaneouslycontacts fresh acid Which is introduced into stage M by means of line 58and additional propane which is introduced into stage M by means of4line 53. Pressure conditions are adjusted in stage M to vaporize propaneat a suflicient rate vin order to remove the heat of reaction as it'isevolved. The temperature of the oil inA stage M thus does notsubstantially change. The vaporized propane is Withdrawn from stage M bymeans of line 40 and handled in any manner desirable, usually by passingto compressor 4I, condenser 42, and then recycling tol the system. Thetreated mixture passes into the bottom of stage M, wherein an acidsludge layer and a treated oil layer separate. The acid sludge layerpasses into stage N in the manner described and contacts fresh untreatedoil; The treated oil is Withdrawn from stage M by means of line 43 andhandled in any manner desirable, usually soda Washed, redistilled and'then passed to motor fuel storage.

The process of the present invention maybe Widely varied.l It may beapplied in the treatmentV of any petroleum oil stock` for the removal ofobjectionable sulphur compounds in which decomposition', polymerization,or side reactions; oocur When treating the same with sulphuric or anequivalent acid. The present invention is particularly applicable in thetreatment of petroleum oil fractions boiling inthe motor fuel boilingrange for the removal of undesirable sulphur compounds and in which itis desired to have essentially substantially no reaction between Vthehydrocarbon constituents and the acid.

An essential feature, of the;- inventionl i's that the heat of reactionbefrem-oved immediately. and' that the temperature of the-oil beingtreated be maintained in the range somevvhat'below about '70 F. InaccordanceZ With the present process, the acid and theI oil Aare dilutedby ther evolved gas which removes the-heatof reaction'throughout themass of liquid as it is formed. 'Ihe evolution of propane throughout themass, furthermore, materially increases the agitation of the mixture andthus prevents local overheating. By operating. in. the, mannerdescribed, the oil may, if desired, be treated for the removal ofobjectionable sulphur compounds at substantially atmospherictemperatures in the range from 70 F. to 85 F. However the preferredoperation is to cool the oil somewhat and to maintain the temperature ofthe cooled oil in this range without any substantial temperature change.By operating in accordance with the present process, very satisfactoryresults are secured by desulphurizing the oil at temperatures in therange from about 65 F. to 70 F., provided the temperature be maintainedconstant and that local overheating be eliminated by the vaporization ofthe refrigerant throughout the mass at the instant the acid contacts theoil. When operating in this manner the oil is cooled prior to contactingthe same with acid so that it is not necessary to chill the oil incontact with the acid and so that a substantial constant temperature ismaintained. It is essential for the present process that the temperatureof the oil being treated upon Contact with the acid does notsubstantially vary. In accordance with the desired modification, thetemperature of the feed oil being treated upon contact with the acidshould not vary over a temperature range over about F., preferably notover 2 F.

Althouhg any suitable refrigerant may be ern ployed, as for example,sulphur dioxide, and the like, I have found that particularly desirableresults are secured, provided the refrigerant be a liquefied normallygaseous hydrocarbon. In gen eral, it is preferred that the refrigerantshould be a saturated hydrocarbon, such as propane. Under certainconditions it may be desirable to employ a refrigerant comprising amixture of propane and butane. However, a particularly desirable solventcomprises ethane free of higher boiling hydrocarbons. It is especiallypreferred that the refrigerant be mixed with the acid before the acidcontacts the oil and that the pressure be reduced when contact issecured, thus immediately removing the heat of the reaction. The amountof refrigerant added to the fresh acid is sufficient to fully remove theentire heat of reaction in the respective stages and to maintain thetemperature at the desired level. If this procedure be carried out,conditions are adjusted so that the correct amount of refrigerant isvaporized in the individual stage at the desired rate to remove the heatof reaction from the respective stage and to maintain the oil atsubstantially a contant temperature. Ho ever, in general, it ispreferred to employ an operation in which the correct amount ofrefrigerant is added in each individual stage in order to remove theheat of reaction from that stage at the desired rate. Another preferredmodification, particularly when employing light petroleum hydrocarbonsas the refrigerant, is to acid treat the oil prior to stabilizing thesame.

The process of the present invention is not to be limited by any theoryor mode of operation, but only in and by the following claim in which itis desired to claim all novelty in so far as the prior art permits.

I claim:

Process for the removal of undesirable sulphur compounds from petroleumoils boiling in the motor fuel boiling range under conditions to retainthe major part of the unsaturated constituents in the treated oil,comprising treating said petroleum oil at a temperature in excess ofabout F. with a mixture comprising sulphuric acid and a liquefiedsaturated normally gaseous hydrocarbon u nder conditions to vaporizesaid liquefied hydrocarbon throughout the mass and to remove the heat ofreaction as it is formed so that temperatures above F. are avoided,whereby excessive polymerization and side reactions are prevented.

JACKSON R. SCHONBERG.

